"I would point out that people like me who support hydrocarbon development don't deny that climate is changing," Barton told his fellow members of a House Energy and Commerce subcommittee. "I think you can have an honest difference of opinion of what's causing that change without automatically being either all in that's all because of mankind or it's all just natural. I think there's a divergence of evidence."

"I would point out that if you're a believer in the Bible, one would have to say the Great Flood is an example of climate change and that certainly wasn't because mankind had overdeveloped hydrocarbon energy," Barton added.

A former chairman of the full House Energy and Commerce Committee and a leading Republican voice on energy policy, Barton has expressed skepticism about man-made global warming in the past. In 2009, he tried to argue that carbon emissions are harmless to the environment, noting how prevalent carbon dioxide is in everyday life.

"CO2 is not a pollutant in any normal definition of the term," Barton said in an interview on C-SPAN.

"The global warming signal is now louder than the noise of random weather," Hansen wrote. "Extremely hot summers have increased noticeably. We can say with high confidence that the recent heat waves in Texas and Russia, and the one in Europe in 2003, which killed tens of thousands, were not natural events -- they were caused by human-induced climate change."

"We need to start reducing emissions significantly, not create new ways to increase them," Hansen continued. "The science of the situation is clear -- it’s time for the politics to follow."

Barton -- who acknowledged Wednesday that he's "a proponent and supporter of the Keystone pipeline" -- has also been an outspoken critic of the Obama administration's delay on Keystone XL, calling the president's decision to postpone a decision "bullsh**."

In March, the State Department held the oil pipeline project to be "environmentally sound," a move that outraged many environmentalists. However, the department made no recommendations on whether Obama should proceed with it.

The following 17 senators all scored under 10 in the League of Conservation Voters' <a href="http://scorecard.lcv.org/sites/scorecard.lcv.org/files/LCV_Scorecard_2012.pdf">2012 National Environmental Scorecard</a>.
The senators' scores are based on 14 votes on bills related to offshore drilling, Gulf restoration, oil subsidies, power plant air pollution and other environmental topics.
While over a dozen senators received fewer than 10 points, 37 senators received over 90 points on LCV's 100-point scale.
(Photo by Alex Wong/Getty Images)